Tunable Thermal Link

Technology Marketing SummaryThermal links are incorporated into everything from frying pans to internal combustion engine spark plugs and heat sinks on integrated circuit boards. Typically, the link’s thermal resistance is fixed and cannot be tuned after manufacture. While the ability to tune electrical resistors is widespread, virtually no tunable thermal resistance link exists, which has held back the development of thermal systems.
DescriptionAlex Zettl, Arun Majumdar and their teams at Lawrence Berkeley National Laboratory have developed telescoped multiwall nanotubes that can be variably controlled, providing the first step toward a fully functional thermal transistor, and removing the main obstacle for heat management and for the processing of phonons as information carriers.

Multiwall nanotubes have a very high intrinsic thermal conductance. If a nanotube is geometrically damaged, its thermal conductance is decreased. The thermal conductance of an individual multiwall carbon nanotube can be controllably and reversibly adjusted by sliding the outer shells in and out of the inner core. The conductance drops dramatically (by 85 percent of the original value) after the length of the tube is extended as the nanotube is telescoped out and the core tubes slide from the remaining “housing.” An exponential increase in the thermal resistance occurs with telescoping distance.

The invention would typically include numbers of multiwall nanotubes connected to a heat source and a heat drain and various means of tuning the overall thermal conductance. Although at present controlled by mechanical actuation, it could also be controlled by a thermal gate utilizing thermal expansion of materials.

Tunable thermal linkDisclosed is a device whereby the thermal conductance of a multiwalled nanostructure such as a multiwalled carbon nanotube (MWCNT) can be controllably and reversibly tuned by sliding one or more outer shells with respect to the inner core. As one example, the thermal conductance of an MWCNT dropped to 15% of the original value after extending the length of the MWCNT by 190 nm. The thermal conductivity returned when the tube was contracted. The device may comprise numbers of multiwalled nanotubes or other graphitic layers connected to a heat source and a heat drain and various means for tuning the overall thermal conductance for applications in structure heat management, heat flow in nanoscale or microscale devices and thermal logic devices.